1. Field of the Invention
The present invention relates, generally, to fuse-protected electrical disconnects for power distribution systems. More particularly, the present invention relates to low voltage, high current electrical disconnects having load side and line side terminals.
2. Description of the Prior Art
Power distribution systems, such as those used in telecommunications applications, often need to deliver low voltage but high current electrical power to devices that require this power to operate. These power systems must provide uninterrupted operation and usually rely on batteries to supply instantaneous back-up power if necessary. In these systems, it is sometimes necessary to disconnect power to various pieces of equipment, or small groups of equipment, so that operators can perform maintenance. It is also necessary to provide overload protection for the equipment on an individual basis, so that operators can diagnose malfunctioning electrical devices.
For these reasons, multiple levels of power distribution are used with larger fused disconnects feeding smaller fused disconnects. For example, a single large fused disconnect, ranging in operation from 600 to 1200 xc3x85, can distribute power to many smaller fused disconnects having loads in the range of 1 to 90 xc3x85 in normal operation. Each of these smaller loads should have their own disconnect as well, so that operators can perform maintenance on a specific load device without interrupting the operation of other load devices. Large power distribution systems including telecommunications systems, which supply many electrical devices, therefore require many individual fused disconnects.
Power system enclosures or power distribution frames are designed to receive a standard sized fused disconnect, which is approximately one inch wide by five inches high. Known fused disconnects typically include a housing having, among other items, a line side terminal connected to a power supply line bar, a single load side terminal that enables an electrical connection to a single load device and a single removable plug-in fuse carrier. Some known disconnects also provide an alarm circuit connected in parallel with the main fuse. The alarm circuit provides either local or remote blown fuse indication.
The cumulative effect of these standard sized disconnects is that they take up a large amount of valuable space within the power system enclosure or distribution frame. Typical enclosures, housing up to 128 individual disconnects in a row, fill up quickly. Furthermore, properly maintained large power systems leave adequate room for additional load devices. Since the size of the disconnect housing has been standardized and distribution frames have been fabricated according to the space requirements of such housings, a need exists to optimize the design of existing disconnect assemblies.
The present invention provides an improved fused disconnect. More specifically, the present invention provides a fusible disconnect that includes a single line side terminal, two independent load side terminals, two independent removable fuse carriers and two independent blown fuse indicators. The common line side terminal provides power to both of the removable fuse carriers. The present invention therefore enables a single, standard sized disconnect to isolate and provide overload protection for two electrical load devices, thus reducing the required number of fused disconnects by one half. The present invention also reduces the required number of line side connections by one half.
To this end, in one embodiment of the present invention, a multiple pole fused disconnect housing includes a line terminal, a plurality of load terminals and a pair of fuse connectors for each load terminal. Each pair of fuse connectors is adapted to receive a fuse.
In an embodiment, the housing has a cavity associated with each pair of fuse connectors and each cavity is adapted to receive a fuse. In an embodiment, the fuses are housed in a carrier and each cavity is adapted to receive a fuse carrier.
In an embodiment, the housing is physically dimensioned to require no more mounting space on a standard power distribution frame than does a standard single fuse housing.
In an embodiment, each pair of connectors electrically communicates with the line terminal and a load terminal. In an embodiment, one connector of each pair electrically communicates with a blown fuse indicator. In an embodiment, the blown fuse indicator includes a light emitting diode.
In another embodiment of the present invention, a multiple pole fused disconnect includes a housing, a line terminal secured to the housing and a plurality of load terminals secured to the housing. The fused disconnect also includes a pair of fuses each electrically communicating with the line terminal and a load terminal.
In an embodiment, the line terminal electrically communicates with a blown fuse indicator. In an embodiment, the fuses are housed in a carrier.
In an embodiment, the housing has a cavity associated with each fuse, wherein the cavities are each adapted to receive either a fuse or a fuse carrier. In an embodiment, the housing has a cavity associated with each fuse, wherein the cavities are each adapted to receive identically sized carriers.
In an embodiment, the fuses have different current ratings. In an embodiment, the fuses have current ratings from one to ninety amps.
In an embodiment, the fuses include blown fuse indicators. In an embodiment, the fuse carriers include fused alarm switches in electrical communication with the fuses.
In an embodiment, the housing is physically dimensioned to require no more mounting space on a standard power distribution frame than does a standard single fuse housing.
In an embodiment, the housing includes a plurality of pairs of fuse connectors, each pair of fuse connectors adapted to electrically communicate with a fuse. In an embodiment, the housing includes a plurality of pairs of conductive clips, each pair of clips adapted to press-fit onto a pair of fuse contacts associated with the fuse.
In a further embodiment of the present invention, a method of providing fuse-protected electrical disconnects for a plurality of individual load-side devices in a power distribution system includes the following steps. An operator connects a single industry-standard size electrical disconnect housing to a power distribution frame, wherein the housing includes one line terminal and a plurality of load terminals. The operator connects a plurality of fuses to the housing, wherein each of the plurality of fuses is in electrical communication with the line terminal and a respective one of the plurality of load terminals. The operator connects the line terminal to line-side power. The operator lastly connects each of the plurality of load terminals to a respective one of the plurality of individual load-side devices.
In this method, the space required along the power distribution frame for the housing is no greater than the space required for a single industry-standard size electrical disconnect. That is, the housing of the present invention requires the same space as those disconnects providing only one line terminal and only one load terminal and being adapted to connect only one fuse therebetween.
An advantage of the present invention is to provide double the amount of electrical devices that can be connected to a standard sized fused disconnect.
Another advantage of the present invention is to reduce the number of required load side connections in a power distribution frame by one half.
A further advantage of the present invention is to provide a housing that is compatible with existing enclosures or power distribution frames.
Yet another advantage of the present invention is to provide individual blown fuse indication for each fuse, as well as to isolate secondary fuse alarms from the housing to reduce the frequency of false alarms.
Additional features and advantages of the present invention will be described in, and apparent from, the following Detailed Description of the preferred embodiments and the Drawings.